there's sonics rising, but i really don't like the format over there. But there's also the RealGM forum, and the inside hoops one, but nothing really dedicated fully to the Seattle Supersonics, they all pretty much disappeared after 2008.
The scout one is still up (though scout stopped listing it with other teams) but its only been myself talking for years seeing if anyone ever would reply. I don't think anyone else even knows its still running.
I'm getting it back going... just trying to figure out which software to use. Used SMF before and I had literally 250 new spam users a day after a week.